1. Field of the Invention
This invention relates to a toothbrush including a handle part, and a brush head carrying cleaning elements that project through a perforated plate. A bristle carrier supports the cleaning elements and the perforated plate, said bristle carrier having a circumference upon which thread webs are formed.
2. Description of the Prior Art
A toothbrush of the above-mentioned type in which the cleaning elements are formed by bundles or tufts of bristles is, for example, known from U.S. Pat. Nos. 4,152,806 and 4,149,293. In this prior-art toothbrush the perforated plate is pivotably supported on the brush body. The distance between the perforated plate and the brush body is varied by the pivotal movement of the perforated plate. As a result, the free length of the ends of the bristle filaments at the use side, i.e. that part of the bristle filaments that projects over the perforated plate, is also changed, so that a change in the stiffness of the bristle filaments is effected by the pivotal movement of the perforated plate relative to the brush body. When the bristle filaments project over the perforated plate with a relatively large length, the stiffness and, as a consequence, the hardness of the brush are low; with a small length, the stiffness is high.
The German Patent No. DE-A-39 28 919 discloses a massage device comprising a pot-shaped basic body and a base member which is also pot-shaped and provided in the basic body in engagement therewith. The base member comprises recesses through which a multitude of massage elements that are formed as bristle tufts are projecting. The ends of the massage elements at the fastening side are received in a mount which is in threaded engagement with the basic body. The distance of the ends of the massage elements at the fastening side is changed relative to the base member by rotating the mount. The base member is received with its annular edge in a correspondingly formed, surrounding annular groove of the basic body and locked to the basic body.
The above-mentioned toothbrushes that are already known from the prior art have the drawback that they do not meet today""s hygienic demands. A wedge-shaped slot in which bacteria and dirt may get stuck is formed between the toothbrush body and the end of the perforated plate at the fastening side. A gap in which dirt may get stuck is also formed in the area of the bristle filaments between the perforated plate and the brush body, so that the brush becomes unsightly after a certain period of use. Moreover, the above-mentioned toothbrushes have the drawback that the free length of all of the bristle filaments projecting through the perforated plate is not changed in a uniform manner due to the pivotal movement of the perforated plate. Rather, the bristle filaments that are more remote from the point of pivotal movement are subjected to a greater change in length than the bristle filaments arranged in the neighborhood of the point of pivotal movement. Depending on the pivotal movement of the perforated plate, this results in a gradient of stiffness within the toothbrush tufting formed by the bristle filaments. The stiffness of the bristle filaments cannot be adjusted in a predeterminable manner with the necessary accuracy in the prior-art brushes.
It is the object of the present invention to provide a toothbrush of adjustable stiffness that satisfies today""s hygienic demands and is still attractive in appearance after a long period of use, and whose stiffness can be adjusted very accurately. It is also the object of the present invention to provide a bristle insert as a replacement and wear part for the toothbrush according to the invention.
According to a more specific object of the invention, the toothbrush includes a handle part, and a brush head carrying cleaning elements that project through a perforated plate. A bristle carrier supports the cleaning elements and the perforated plate, said bristle carrier having a circumference upon which thread webs are formed.
Thanks to the perforated plate which is rotatably held on the brush body, the brush body is closed relative to the ends of the bristle filaments at the fastening side. The filaments are held in a bristle carrier which is in threaded engagement with the brush body. For changing the stiffness the bristle carrier is rotated relative to the brush body so that the bristle carrier travels relative to the brush body according to the thread pitch in the axial direction of a hole which accommodates the bristle carrier. The perforated plate just follows the rotation of the bristle carrier, thereby effecting a change in the stiffness of the cleaning elements without creating an open gap between the perforated plate and the brush body where dirt may collect. Thanks to the threaded engagement the bristle carrier changes its position relative to the perforated plate altogether, so that all of the cleaning elements held on the bristle carrier are uniformly changed with respect to their length. Thus the stiffness of all of the cleaning elements projecting beyond the perforated plate, which cleaning elements are e.g. formed by bristle filaments, is identically changed as well. Moreover, the brush of the invention has the further advantage that the desired stiffness of the bristle filaments can be adjusted accurately by rotating the bristle carrier.
Under hygienic aspects it is preferred that the perforated plate ends flush with the upper side of the brush body. Thanks to this measure a smooth surface is created on the surface of the brush in the area of those bristles whose stiffness can be varied.
Preferably, the brush body has further provided thereon an annular groove in which the perforated plate is detachably and rotatably held. Preferably, the detachable connection between perforated plate and brush body is created by a lock type connection. The perforated plate can thus be removed from the brush body and the bristle carrier can be rotated out of the brush body to replace worn bristle filaments held on the bristle carrier. If all of the bristle filaments of the toothbrush are arranged on the one or several bristle carriers, the whole toothbrush need not be replaced upon wear of all of the bristle filaments, but it is only necessary to replace the bristle carrier carrying the bristle filaments and, preferably, the perforated plate through which the bristle filaments are projecting.
The bristle carrier is detachably connected to the brush body, preferably together with the perforated plate. Such a detachable unit creates a bristle insert which can be inserted into the brush body as a replacement part. The detachable connection between the perforated plate and the brush body is preferably established by a lock type connection which is designed such that the bristle carrier is pressed against the perforated plate by applying pressure to said carrier, and the perforated plate can be removed together with the bristle carrier from the brush body.
Preferably, at least two thread webs are provided on the bristle carrier and distributed over the circumference thereof, with guide grooves being provided for the thread webs between the perforated plate arid a thread formed on the brush body. With such a configuration only the thread webs must be brought into alignment with the corresponding grooves and the bristle carriers must then be pressed together with the perforated plate into the brush body, whereby the insertion of the bristle carrier is, in particular, simplified during replacement of a bristle carrier with worn bristle filaments together with the perforated plate.
Bristle carrier and perforated plate are preferably removed in a simplified way in that the respective insertion grooves are in alignment with the end of the thread turns for the threaded pins. Upon rotation of the bristle carrier in such a way that said carrier moves towards the perforated plate, the thread webs in an end position will impinge on a boundary surface formed on the brush body for the thread. This boundary surface is in alignment with a respective side surface of a guide groove, so that the thread webs in the end position come to rest in the insertion grooves and the bristle carrier in said end position can be removed from the brush body by a mere axial displacement towards the perforated plate.
According to a further preferred development of the present invention, a hardness scale is provided on the face of the bristle carrier that faces away from the bristle filaments, so that the user of the brush is enabled to adjust a desired stiffness of the bristle filaments in a predeterminable way.
For the adjustment of the stiffness the bristle carrier may be connected to a knurled ring which at least in part projects over the portion of the brush body which surrounds the bristle carrier. Under hygienic aspects, however, it is preferred that, instead of such a knurled ring on the face of the bristle carrier facing away from the bristle filaments, a grip portion is provided, for instance for the fingers of a user. For an easy handling, however, it is preferred that the grip portion is designed such that a bristle carrier tool can be brought into operative communication with the bristle carrier. Such a bristle carrier tool is preferably detachably connected to the brush body, so that the bristle carrier tool can be gripped any time. Moreover, the brush body is made longer by the detachable bristle carrier tool connected thereto, so that the brush can be handled more easily on the whole.
Furthermore, the present invention relates to a bristle insert for a toothbrush of the above-mentioned type, comprising a bristle carrier carrying cleaning elements, the circumferential surface of which has formed thereon thread webs, as well as a perforated plate through which the cleaning elements are projecting. Such a bristle insert is suited as a replacement part for the above-mentioned toothbrush, which may also be an electrically driven toothbrush. Preferred developments of the bristle insert are indicated in the dependent claims.